### 第一段

1 .Listen to part of a lecture in an astronomy class.

2 .You will not need to remember the numbers the professor mentions.

### 第二段

1 .OK. Let's get going.

2 .Today I'm going to talk about how the asteroid belt was discovered.

3 .And... I'm going to start by writing some numbers on the board.

4 .Here they are; We'll start with zero, then 3, ... 6, ... 12.

5 .Uh, tell me what I'm doing.

### 第三段

1 .Multiplying by 2?

（所得值）乘以2？

2 .Right, I'm doubling the numbers, so 2 times 12 is 24, and the next one I'm going to write after 24 would be...

1 .48.

48

### 第五段

1 .48. Then 96.

48。然后是96。

2 .We'll stop there for now.

3 .Uh, now I'll write another row of numbers under that.

4 .Tell me what I'm doing.

5 .4, 7, 10... How am I getting the second row?

4,7,10……第二组数字我是怎么得到的？

### 第六段

1 .Adding 4 to the numbers in the first row.

### 第七段

1 .I'm adding 4 to each number in the first row to give you a second row.

2 .So the last two will be 52, 100, and now tell me what I'm doing.

### 第八段

1 .Putting in a decimal?

### 第九段

1 .Yes, I divided all those numbers by 10 by putting in a decimal point.

2 .Now I'm going to write the names of the planets under the numbers.

3 .Mercury... Venus... Earth... Mars.

4 .So, what do the numbers mean?

5 .Do you remember from the reading?

### 第十段

1 .Is it the distance of the planets from the Sun?

### 第十一段

1 .Right. In astronomical units - not perfect, but tantalizingly close.

2 .The value for Mars is off by... 6 or 7 percent or so.

3 .It's... but it's within 10 percent of the average distance to Mars from the Sun.

4 .But I kind of have to skip the one after Mars for now.

5 .Then Jupiter's right there at 5-point something, and then Saturn is about 10 astronomical units from the Sun.

6 .Um, well, this pattern is known as Bode's Law.

### 第十二段

1 .Um, it isn't really a scientific law, not in the sense of predicting gravitation mathematically or something, but it's attempting a pattern in the spacing of the planets, and it was noticed by Bode hundreds of years ago.

2 .Well, you can imagine that there was some interest in why the 2.8 spot in the pattern was skipped, and um... but there wasn't anything obvious there, in the early telescopes.

3 .Then what happened in the late 1700s?

4 .The discovery of...?

### 第十三段

1 .Another planet?

### 第十四段

1 .The next planet out, Uranus - after Saturn.

### 第十五段

1 .And look, Uranus fits in the next spot in the pattern pretty nicely, um, not perfectly, but close.

2 .And so then people got really excited about the validity of this thing and finding the missing object between Mars and Jupiter.

3 .And telescopes, remember, were getting better.

4 .So people went to work on finding objects that would be at that missing distance from the Sun, and then in 1801, the object Ceres was discovered.

### 第十六段

1 .And Ceres was in the right place - the missing spot.

2 .Uh, but it was way too faint to be a planet.

3 .It looked like a little star.

4 .Uh, and because of its star-like appearance, um, it was called an "asteroid".

5 .OK? "Aster" is Greek for "star", as in "astronomy".

6 .Um, and so, Ceres was the first and is the largest of what became many objects discovered at that same distance.

7 .Not just one thing, but all the objects found at that distance form the asteroid belt.

8 .So the asteroid belt is the most famous success of this Bode's Law.

9 .That's how the asteroid belt was discovered.